U.S. patent number 10,286,892 [Application Number 15/896,412] was granted by the patent office on 2019-05-14 for autonomous motor control during loss of motor communications.
This patent grant is currently assigned to FORD GLOBAL TECHNOLOGIES, LLC. The grantee listed for this patent is Ford Global Technologies, LLC. Invention is credited to Paul Stephen Bryan, Rajit Johri, Brian Francis Morton, Fazal Urrahman Syed.
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United States Patent |
10,286,892 |
Johri , et al. |
May 14, 2019 |
Autonomous motor control during loss of motor communications
Abstract
A computer-implemented method includes, responsive to absence of
a motor controller receiving communication packets for a
predetermined time during a drive cycle, operating by the
controller (i) an inverter to output voltage at a setpoint defined
by an inverter terminal voltage at expiration of the predetermined
time, and (ii) a motor coupled with the inverter to apply torque
according to a change in the voltage.
Inventors: |
Johri; Rajit (Canton, MI),
Syed; Fazal Urrahman (Canton, MI), Bryan; Paul Stephen
(Saline, MI), Morton; Brian Francis (Dearborn, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
FORD GLOBAL TECHNOLOGIES, LLC
(Dearborn, MI)
|
Family
ID: |
66439496 |
Appl.
No.: |
15/896,412 |
Filed: |
February 14, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L
15/20 (20130101); B60W 10/26 (20130101); B60L
3/0084 (20130101); H02P 3/06 (20130101); H02P
6/06 (20130101); B60W 10/24 (20130101); B60W
20/50 (20130101); B60K 6/48 (20130101); B60K
6/26 (20130101); H02P 23/14 (20130101); B60L
3/0061 (20130101); B60W 10/08 (20130101); B60L
2260/44 (20130101); B60L 2240/423 (20130101); B60L
2240/527 (20130101); B60W 50/035 (20130101); B60W
50/038 (20130101); B60K 2006/4825 (20130101); B60L
2240/549 (20130101); B60W 2510/244 (20130101); Y02T
10/7275 (20130101); B60L 2240/443 (20130101); Y02T
10/645 (20130101); B60L 2240/42 (20130101); B60W
2710/083 (20130101); Y02T 10/6221 (20130101); Y02T
10/642 (20130101); Y02T 10/6252 (20130101); B60L
2240/80 (20130101); Y02T 90/16 (20130101) |
Current International
Class: |
H02P
1/46 (20060101); B60L 15/20 (20060101); H02P
6/06 (20060101); H02P 23/14 (20060101); B60K
6/26 (20071001); B60W 10/24 (20060101); B60L
3/00 (20190101); H02P 3/06 (20060101); B60W
10/08 (20060101); H02P 3/18 (20060101); H02P
6/00 (20160101); H02P 1/50 (20060101) |
Field of
Search: |
;318/715 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Glass; Erick D
Attorney, Agent or Firm: Kelley; David Brooks Kushman
P.C.
Claims
What is claimed is:
1. A vehicle comprising: a motor; an inverter; and a motor
controller configured to, responsive to an absence of receiving
communication packets for a predetermined time during a drive
cycle, operate the inverter to output voltage at a setpoint defined
by a terminal voltage of the inverter at expiration of the
predetermined time, the motor configured to apply torque according
to a change in the voltage.
2. The vehicle of claim 1 further comprising a traction battery,
wherein the terminal voltage is measured across terminals coupling
the inverter to the traction battery responsive to the motor
providing a propulsive force.
3. The vehicle of claim 2 further comprising an auxiliary battery
and a DC converter configured to equalize voltage between the
traction battery and an auxiliary battery.
4. The vehicle of claim 1 further comprising an engine, a traction
battery, and an engine controller configured to, responsive to
absence of receiving communication packets from the motor
controller for the predetermined time, operate the engine based on
a current of the traction battery.
5. The vehicle of claim 4, wherein the engine controller is further
configured to, responsive to the absence of receiving communication
packets from the motor controller for the predetermined time,
inhibit automatic stop-start operation of the engine.
6. The vehicle of claim 4, wherein the engine controller is further
configured to, responsive to the absence of receiving communication
packets from the motor controller for the predetermined time while
the engine is not operating, start the engine.
7. The vehicle of claim 1, wherein the motor is further configured
to apply the torque according to an estimated traction battery
state of charge.
8. A hybrid vehicle, comprising: a motor; an engine; a traction
battery; and an engine controller configured to, responsive to an
absence of receiving communication packets from a motor controller
for a predetermined time during a drive cycle, operate the engine
according to a current of the traction battery.
9. The hybrid vehicle of claim 8 further comprising an inverter and
a motor controller configured to operate the inverter to output
voltage at a setpoint defined by a terminal voltage of the inverter
at expiration of the predetermined time, the motor configured to
apply torque according to a change in the terminal voltage.
10. The hybrid vehicle of claim 9, wherein the terminal voltage is
measured across terminals coupling the inverter and traction
battery responsive to the motor providing a propulsive force.
11. The hybrid vehicle of claim 8, wherein the engine controller is
further configured to, responsive to the absence, inhibit
stop-start operation of the engine.
12. The hybrid vehicle of claim 8, wherein the engine controller is
further configured to, responsive to the absence while the engine
is not operating, start the engine.
13. A computer-implemented method comprising: responsive to absence
of a motor controller receiving communication packets for a
predetermined time during a drive cycle, operating by the
controller an inverter to output voltage at a setpoint defined by
an inverter terminal voltage at expiration of the predetermined
time, and a motor coupled with the inverter to apply torque
according to a change in the voltage.
14. The method of claim 13 further comprising, responsive to an
absence of an engine controller receiving communication packets
from the motor controller for the predetermined time, operating an
engine according to a current of a traction battery.
15. The method of claim 14 further comprising responsive to the
absence of the engine controller receiving communication packets
from the motor controller for the predetermined time while the
engine is not operating, starting the engine.
16. The method of claim 15 further comprising responsive to the
absence of the engine controller receiving communication packets
from the motor controller for the predetermined time, inhibiting
engine stop-start operation.
Description
TECHNICAL FIELD
This application is generally related to an electric motor system
configured to operate during a loss of communication event between
the electric motor system and a vehicle network.
BACKGROUND
Hybrid electric vehicles (HEVs) include an internal combustion
engine, an electric machine such as an electric motor, and a
traction battery. In these vehicles, signals are sent and received
over at least one vehicle network. The electric motor system
receives critical information over the vehicle network, including
the motor torque necessary to meet vehicle performance requirements
and driver demand. In the event of a loss of communication between
the electric motor system and the vehicle network, several actions
may be necessary to ensure continued operation of the vehicle.
Since shutdown of the entire vehicle may be undesirable, limited
operation strategy (LOS) modes can be implemented to prolong
vehicle operation.
SUMMARY
A vehicle includes a motor, an inverter, and a motor controller.
The motor controller may be configured to, responsive to an absence
of receiving communication packets for a predetermined time during
a drive cycle, operate the inverter to output voltage at a setpoint
defined by a terminal voltage of the inverter at expiration of the
predetermined time, the motor configured to apply torque according
to a change in the voltage.
A hybrid vehicle includes a motor, an engine, a traction battery,
and an engine controller. The engine controller may be configured
to, responsive to an absence of receiving communication packets
from a motor controller for a predetermined time during a drive
cycle, operate the engine according to a current of the traction
battery.
A computer-implemented method includes, responsive to absence of a
motor controller receiving communication packets for a
predetermined time during a drive cycle, operating by the
controller (i) an inverter to output voltage at a setpoint defined
by an inverter terminal voltage at expiration of the predetermined
time, and (ii) a motor coupled with the inverter to apply torque
according to a change in the voltage.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a hybrid vehicle illustrating typical
drivetrain and energy storage components including a variable
voltage variable frequency converter.
FIG. 2 is a block diagram of a vehicular powertrain control
system.
FIG. 3 is a schematic diagram of a hybrid electric vehicle
(HEV).
FIG. 4 is a schematic diagram of the electric power connections in
a HEV power system.
FIG. 5 is a flow diagram of a vehicle control system during a loss
of motor communications.
DETAILED DESCRIPTION
Embodiments of the present disclosure are described herein. It is
to be understood, however, that the disclosed embodiments are
merely examples and other embodiments can take various and
alternative forms. The figures are not necessarily to scale; some
features could be exaggerated or minimized to show details of
particular components. Therefore, specific structural and
functional details disclosed herein are not to be interpreted as
limiting, but merely as a representative basis for teaching one
skilled in the art to variously employ the embodiments. As those of
ordinary skill in the art will understand, various features
illustrated and described with reference to any one of the figures
can be combined with features illustrated in one or more other
figures to produce embodiments that are not explicitly illustrated
or described. The combinations of features illustrated provide
representative embodiments for typical applications. Various
combinations and modifications of the features consistent with the
teachings of this disclosure, however, could be desired for
particular applications or implementations.
Often vehicles include multiple modules (e.g., controllers) each
performing specific tasks and often each module requires data from
a different module to perform effectively. In some instances, a
loss of communication between two modules may result in a shutdown
of the vehicle after which the vehicle is inoperable until the loss
of communication is restored. Often, the communication includes the
transfer of data packets, the packets may include a source ID, a
destination ID, a header, a body (e.g., data), an error checking
field (e.g., checksum), etc. For example, after a loss of
communication with a motor control unit (MCU), the electric motor
may not be able to be used to charge a traction
battery/high-voltage battery that in turn would restrict charging
of a 12V low-voltage battery. As such, the traction battery may
eventually become depleted due to use of high-voltage loads (e.g.,
air-conditioning load, DC/DC), followed by the 12V battery,
resulting in a power down of the 12V bus. Once the 12V bus powers
down, modules on the bus (e.g., Engine Control Unit (ECU)) may also
power down and the Internal Combustion Engine controlled by the ECU
would be shut down resulting in a shutdown of the vehicle (e.g.,
quit on road (QoR).
Here, a strategy is provided to continue to operate a vehicle when
a controller (such as an MCU) loses communication (e.g., CAN,
Ethernet, or Flexray communication). In one illustration, an MCU
loses communication with all modules including a Battery Control
Module (BECM). Loss of BECM communication is a more restrictive
failure and hence, is a superset of other possible scenarios for
example, an MCU partial CAN communication loss.
Here, the MCU operates the motor independently (i.e., without a
torque command received from a vehicle system controller (VSC)). In
a lost communication scenario, the MCU enters into an inverter
voltage maintenance mode (i.e., a desired motor torque is based on
a feedback controller to maintain an inverter voltage at a desired
set point. The VSC uses traction battery current and traction
battery voltage to estimate a motor torque in an absence of actual
feedback from MCU monitoring the motor. The VSC then corrects the
requested engine torque based on the estimated motor torque. This
ensures engine produces enough torque to meet driver demand as well
as to compensate for the electric motor load.
FIG. 1 depicts an electrified vehicle 112 that may be referred to
as a plug-in hybrid-electric vehicle (PHEV). A plug-in
hybrid-electric vehicle 112 may comprise one or more electric
machines 114 mechanically coupled to a hybrid transmission 116. The
electric machines 114 may be capable of operating as a motor or a
generator. In addition, the hybrid transmission 116 is mechanically
coupled to an engine 118. The hybrid transmission 116 is also
mechanically coupled to a drive shaft 120 that is mechanically
coupled to the wheels 122. The electric machines 114 can provide
propulsion and deceleration capability when the engine 118 is
turned on or off. The electric machines 114 may also act as
generators and can provide fuel economy benefits by recovering
energy that would normally be lost as heat in a friction braking
system. The electric machines 114 may also reduce vehicle emissions
by allowing the engine 118 to operate at more efficient speeds and
allowing the hybrid-electric vehicle 112 to be operated in electric
mode with the engine 118 off under certain conditions. An
electrified vehicle 112 may also be a battery electric vehicle
(BEV). In a BEV configuration, the engine 118 may not be present.
In other configurations, the electrified vehicle 112 may be a full
hybrid-electric vehicle (FHEV) without plug-in capability.
A traction battery or battery pack 124 stores energy that can be
used by the electric machines 114. The vehicle battery pack 124 may
provide a high-voltage direct current (DC) output. The traction
battery 124 may be electrically coupled to one or more power
electronics modules 126. One or more contactors 142 may isolate the
traction battery 124 from other components when opened and connect
the traction battery 124 to other components when closed. The power
electronics module 126 is also electrically coupled to the electric
machines 114 and provides the ability to bi-directionally transfer
energy between the traction battery 124 and the electric machines
114. For example, a traction battery 124 may provide a DC voltage
while the electric machines 114 may operate with a three-phase
alternating current (AC) to function. The power electronics module
126 may convert the DC voltage to a three-phase AC current to
operate the electric machines 114. In a regenerative mode, the
power electronics module 126 may convert the three-phase AC current
from the electric machines 114 acting as generators to the DC
voltage compatible with the traction battery 124.
The vehicle 112 may include a variable-voltage converter (VVC) 152
electrically coupled between the traction battery 124 and the power
electronics module 126. The VVC 152 may be a DC/DC boost converter
configured to increase or boost the voltage provided by the
traction battery 124. By increasing the voltage, current
requirements may be decreased leading to a reduction in wiring size
for the power electronics module 126 and the electric machines 114.
Further, the electric machines 114 may be operated with better
efficiency and lower losses.
In addition to providing energy for propulsion, the traction
battery 124 may provide energy for other vehicle electrical
systems. The vehicle 112 may include a DC/DC converter module 128
that converts the high-voltage DC output of the traction battery
124 to a low voltage DC supply that is compatible with low-voltage
vehicle loads. An output of the DC/DC converter module 128 may be
electrically coupled to an auxiliary battery 130 (e.g., 12V
battery) for charging the auxiliary battery 130. The low-voltage
systems may be electrically coupled to the auxiliary battery 130.
One or more electrical loads 146 may be coupled to the high-voltage
bus. The electrical loads 146 may have an associated controller
that operates and controls the electrical loads 146 when
appropriate. Examples of electrical loads 146 may be a fan, an
electric heating element and/or an air-conditioning compressor.
The electrified vehicle 112 may be configured to recharge the
traction battery 124 from an external power source 136. The
external power source 136 may be a connection to an electrical
outlet. The external power source 136 may be electrically coupled
to a charger or electric vehicle supply equipment (EVSE) 138. The
external power source 136 may be an electrical power distribution
network or grid as provided by an electric utility company. The
EVSE 138 may provide circuitry and controls to regulate and manage
the transfer of energy between the power source 136 and the vehicle
112. The external power source 136 may provide DC or AC electric
power to the EVSE 138. The EVSE 138 may have a charge connector 140
for plugging into a charge port 134 of the vehicle 112. The charge
port 134 may be any type of port configured to transfer power from
the EVSE 138 to the vehicle 112. The charge port 134 may be
electrically coupled to a charger or on-board power conversion
module 132. The power conversion module 132 may condition the power
supplied from the EVSE 138 to provide the proper voltage and
current levels to the traction battery 124. The power conversion
module 132 may interface with the EVSE 138 to coordinate the
delivery of power to the vehicle 112. The EVSE connector 140 may
have pins that mate with corresponding recesses of the charge port
134. Alternatively, various components described as being
electrically coupled or connected may transfer power using a
wireless inductive coupling.
One or more wheel brakes 144 may be provided for decelerating the
vehicle 112 and preventing motion of the vehicle 112. The wheel
brakes 144 may be hydraulically actuated, electrically actuated, or
some combination thereof. The wheel brakes 144 may be a part of a
brake system 150. The brake system 150 may include other components
to operate the wheel brakes 144. For simplicity, the figure depicts
a single connection between the brake system 150 and one of the
wheel brakes 144. A connection between the brake system 150 and the
other wheel brakes 144 is implied. The brake system 150 may include
a controller to monitor and coordinate the brake system 150. The
brake system 150 may monitor the brake components and control the
wheel brakes 144 for vehicle deceleration. The brake system 150 may
respond to driver commands and may also operate autonomously to
implement features such as stability control. The controller of the
brake system 150 may implement a method of applying a requested
brake force when requested by another controller or
sub-function.
Electronic modules in the vehicle 112 may communicate via one or
more vehicle networks. The vehicle network may include a plurality
of channels for communication. One channel of the vehicle network
may be a serial bus such as a Controller Area Network (CAN). One of
the channels of the vehicle network may include an Ethernet network
defined by Institute of Electrical and Electronics Engineers (IEEE)
802 family of standards. Additional channels of the vehicle network
may include discrete connections between modules and may include
power signals from the auxiliary battery 130. Different signals may
be transferred over different channels of the vehicle network. For
example, video signals may be transferred over a high-speed channel
(e.g., Ethernet) while control signals may be transferred over CAN
or discrete signals. The vehicle network may include any hardware
and software components that aid in transferring signals and data
between modules. The vehicle network is not shown in FIG. 2 but it
may be implied that the vehicle network may connect to any
electronic module that is present in the vehicle 112. A vehicle
system controller (VSC) 148 may be present to coordinate the
operation of the various components.
Often the VVC 152 is configured as a boost converter. The VVC 152
may include input terminals that may be coupled to terminals of the
traction battery 124 through the contactors 142. The VVC 152 may
include output terminals coupled to terminals of the power
electronics module 126. The VVC 152 may be operated to cause a
voltage at the output terminals to be greater than a voltage at the
input terminals. The vehicle 112 may include a VVC controller that
monitors and controls electrical parameters (e.g., voltage and
current) at various locations within the VVC 152. In some
configurations, the VVC controller may be included as part of the
VVC 152. The VVC controller may determine an output voltage
reference, V*.sub.dc. The VVC controller may determine, based on
the electrical parameters and the voltage reference, V*.sub.dc, a
control signal sufficient to cause the VVC 152 to achieve the
desired output voltage. In some configurations, the control signal
may be implemented as a pulse-width modulated (PWM) signal in which
a duty cycle of the PWM signal is varied. The control signal may be
operated at a predetermined switching frequency. The VVC controller
may command the VVC 152 to provide the desired output voltage using
the control signal. The particular control signal at which the VVC
152 is operated may be directly related to the amount of voltage
boost to be provided by the VVC 152.
With reference to FIG. 1, the VVC 152 may boost or "step up" the
voltage potential of the electrical power provided by the traction
battery 124. The traction battery 124 may provide high-voltage (HV)
DC power. In some configurations, the traction battery 124 may
provide a voltage between 150 and 400 Volts. The contactor 142 may
be electrically coupled in series between the traction battery 124
and the VVC 152. When the contactor 142 is closed, the HV DC power
may be transferred from the traction battery 124 to the VVC 152. An
input capacitor may be electrically coupled in parallel to the
traction battery 124. The input capacitor may reduce any voltage
and current ripple. The VVC 152 may receive the HV DC power and
boost or "step up" the voltage potential of the input voltage
according to the duty cycle. Often an output capacitor is
electrically coupled between the output terminals of the VVC 152
and the input of the power electronics module 126 to stabilize the
bus voltage and reduce voltage and current ripple at the output of
the VVC 152.
FIG. 2 is a block diagram illustrating an example vehicle control
system for a vehicle (e.g., vehicle 112 or vehicle 310 of FIG. 3).
As shown, vehicle control system 202 receives signals and/or
commands generated by driver inputs 200 (e.g., gear selection,
accelerator position, and braking effort). The vehicle control
system 202 processes these driver inputs 200 and communicates
commands throughout the vehicle. The vehicle control system 202 may
be electrically connected to various other powertrain control
systems 204-208, such as the engine control system 204, M/G control
system 206, and battery control system 208, for example, and may
act as an overall controller of the vehicle. The vehicle control
system 202 may be electrically connected to and communicate with
various powertrain control systems 204-208 over a vehicle network
210. The vehicle network 210 continuously broadcasts data and
information to the powertrain control systems 204-208. The vehicle
network 210 may be a controlled area network (CAN) bus, Flexray
bus, Ethernet bus, or other vehicle communication bus used to pass
data to and from the vehicle control system 202 and other various
controllers, subsystems or components thereof.
In hybrid vehicles, the motor system receives critical information
over the vehicle network. Signals such as a desired torque, mode of
operation, and other critical signals are sent and received on this
network. In the event of a loss of communication between the motor
system and vehicle network, several actions may be necessary to
ensure continued operation of the vehicle. Since shutdown of the
entire vehicle may be undesirable, limited operation strategy (LOS)
modes can be implemented to prolong the operation of the
vehicle.
Referring to FIG. 3, a schematic diagram of a hybrid electric
vehicle (HEV) 310 is illustrated according to an embodiment of the
present disclosure. FIG. 3 illustrates representative relationships
among the components. Physical placement and orientation of the
components within the vehicle may vary. The HEV 310 includes a
powertrain 312. The powertrain 312 includes an engine 314 that
drives a transmission 316, which may be referred to as a modular
hybrid transmission (MHT). As will be described in further detail
below, transmission 316 includes an electric machine such as an
electric motor/generator (M/G) 318, an associated traction battery
320, a torque converter 322, and a multiple step-ratio automatic
transmission, or gearbox 324. The engine 314, M/G 318, torque
converter 322, and the automatic transmission 316 are connected
sequentially in series, as illustrated in FIG. 3.
The engine 314 and the M/G 318 are both drive sources for the HEV
310. The engine 314 generally represents a power source that may
include an internal combustion engine such as a gasoline, diesel,
or natural gas-powered engine, or a fuel cell. The engine 314
generates an engine power and corresponding engine torque that is
supplied to the M/G 318 when a disconnect clutch 326 between the
engine 314 and the M/G 318 is at least partially engaged. The M/G
318 may be implemented by any one of a plurality of types of
electric machines. For example, M/G 318 may be a permanent magnet
synchronous motor. Power electronics condition direct current (DC)
power provided by the battery 320 to the requirements of the M/G
318, as will be described below. For example, power electronics may
provide three-phase alternating current (AC) to the M/G 318.
When the disconnect clutch 326 is at least partially engaged, power
flow from the engine 314 to the M/G 318 or from the M/G 318 to the
engine 314 is possible. For example, the disconnect clutch 326 may
be engaged and M/G 318 may operate as a generator to convert
rotational energy provided by a crankshaft 28 and M/G shaft 330
into electrical energy to be stored in the battery 320. The
disconnect clutch 326 can also be disengaged to isolate the engine
314 from the remainder of the powertrain 312 such that the M/G 318
can act as the sole drive source for the HEV 310. Shaft 330 extends
through the M/G 318. The M/G 318 is continuously drivably connected
to the shaft 330, whereas the engine 314 is drivably connected to
the shaft 330 only when the disconnect clutch 326 is at least
partially engaged.
A separate starter motor 331 can be selectively engaged with the
engine 314 to rotate the engine to allow combustion to begin. Once
the engine is started, the starter motor 331 can be disengaged from
the engine via, for example, a clutch (not shown) between the
starter motor 331 and the engine 314. In one embodiment, the engine
314 is started by the starter motor 331 while the disconnect clutch
326 is open, keeping the engine disconnected with the M/G 318. Once
the engine has started and is brought up to speed with the M/G 318,
the disconnect clutch 326 can couple the engine to the M/G to allow
the engine to provide drive torque.
In another embodiment, the starter motor 331 is not provided and,
instead, the engine 314 is started by the M/G 318. To do so, the
disconnect clutch 326 partially engages to transfer torque from the
M/G 318 to the engine 314. The M/G 318 may be required to ramp up
in torque to fulfill driver demands while also starting the engine
314. The disconnect clutch 326 can then be fully engaged once the
engine speed is brought up to the speed of the M/G.
The M/G 318 is connected to the torque converter 322 via shaft 330.
The torque converter 322 is therefore connected to the engine 314
when the disconnect clutch 326 is at least partially engaged. The
torque converter 322 includes an impeller fixed to M/G shaft 330
and a turbine fixed to a transmission input shaft 32. The torque
converter 322 thus provides a hydraulic coupling between shaft 330
and transmission input shaft 32. The torque converter 322 transmits
power from the impeller to the turbine when the impeller rotates
faster than the turbine. The magnitude of the turbine torque and
impeller torque generally depend upon the relative speeds. When the
ratio of impeller speed to turbine speed is sufficiently high, the
turbine torque is a multiple of the impeller torque. A torque
converter bypass clutch 334 may also be provided that, when
engaged, frictionally or mechanically couples the impeller and the
turbine of the torque converter 322, permitting more efficient
power transfer. The torque converter bypass clutch 334 may be
operated as a launch clutch to provide smooth vehicle launch.
Alternatively, or in combination, a launch clutch similar to
disconnect clutch 326 may be provided between the M/G 318 and
gearbox 324 for applications that do not include a torque converter
322 or a torque converter bypass clutch 334. In some applications,
disconnect clutch 326 is generally referred to as an upstream
clutch and launch clutch 334 (which may be a torque converter
bypass clutch) is generally referred to as a downstream clutch.
The gearbox 324 may include gear sets (not shown) that are
selectively placed in different gear ratios by selective engagement
of friction elements such as clutches and brakes (not shown) to
establish the desired multiple discrete or step drive ratios. The
friction elements are controllable through a shift schedule that
connects and disconnects certain elements of the gear sets to
control the ratio between a transmission output shaft 336 and the
transmission input shaft 332. The gearbox 324 is automatically
shifted from one ratio to another based on various vehicle and
ambient operating conditions by an associated controller, such as a
powertrain control unit (PCU). The gearbox 324 then provides
powertrain output torque to output shaft 336.
The hydraulically controlled gearbox 324 used with a torque
converter 322 is but one example of a gearbox or transmission
arrangement; any multiple ratio gearbox that accepts input
torque(s) from an engine and/or a motor and then provides torque to
an output shaft at the different ratios is acceptable for use with
embodiments of the present disclosure. For example, gearbox 324 may
be implemented by an automated mechanical (or manual) transmission
(AMT) that includes one or more servo motors to translate/rotate
shift forks along a shift rail to select a desired gear ratio. For
example, an AMT may be used in applications with higher torque
requirements, for example.
As shown in FIG. 1, the output shaft 336 is connected to a
differential 340. The differential 340 drives a pair of wheels 342
via respective axles 344 connected to the differential 340. The
differential transmits approximately equal torque to each wheel 342
while permitting slight speed differences such as when the vehicle
turns a corner. Different types of differentials or similar devices
may be used to distribute torque from the powertrain to one or more
wheels. For example, in some applications, torque distribution may
vary depending on the particular operating mode or condition.
The powertrain 312 further includes an associated controller 350
such as a powertrain control unit (PCU). While illustrated as one
controller, the controller 350 may be part of a larger control
system and may be controlled by various other controllers
throughout the vehicle 310, such as a vehicle system controller
(VSC). Separate additional controllers and their hierarchy will be
described in more detail in FIG. 2. It should therefore be
understood that the powertrain control unit 350 and one or more
other controllers can collectively be referred to as a "controller"
that controls various actuators in response to signals from various
sensors to control functions such as starting/stopping, operating
M/G 318 to provide wheel torque or charge battery 320, select or
schedule transmission shifts, etc. Controller 350 may include a
microprocessor or central processing unit (CPU) in communication
with various types of computer readable storage devices or media.
Computer readable storage devices or media may include volatile and
nonvolatile storage in read-only memory (ROM), random-access memory
(RAM), and keep-alive memory (KAM), for example. KAM is a
persistent or non-volatile memory that may be used to store various
operating variables while the CPU is powered down.
Computer-readable storage devices or media may be implemented using
any of a number of known memory devices such as PROMs (programmable
read-only memory), EPROMs (electrically PROM), EEPROMs
(electrically erasable PROM), flash memory, or any other electric,
magnetic, optical, or combination memory devices capable of storing
data, some of which represent executable instructions, used by the
controller in controlling the engine or vehicle.
The controller communicates with various engine/vehicle sensors and
actuators via an input/output (I/O) interface that may be
implemented as a single integrated interface that provides various
raw data or signal conditioning, processing, and/or conversion,
short-circuit protection, and the like. Alternatively, one or more
dedicated hardware or firmware chips may be used to condition and
process particular signals before being supplied to the CPU. As
generally illustrated in the representative embodiment of FIG. 1,
controller 350 may communicate signals to and/or from engine 314,
disconnect clutch 326, M/G 318, launch clutch 334, transmission
gearbox 324, and power electronics 356. Although not explicitly
illustrated, often various functions or components may be
controlled by controller 350 within each of the subsystems
identified above. Examples of parameters, systems, and/or
components that may be directly or indirectly actuated using
control logic executed by the controller include fuel injection
timing, rate, and duration, throttle valve position, spark plug
ignition timing (for spark-ignition engines), intake/exhaust valve
timing and duration, front-end accessory drive (FEAD) components
such as an alternator, air conditioning compressor, battery
charging, regenerative braking, M/G operation, clutch pressures for
disconnect clutch 326, launch clutch 334, and transmission gearbox
324, and the like. Sensors communicating input through the I/O
interface may be used to indicate turbocharger boost pressure,
crankshaft position (PIP), engine rotational speed (RPM), wheel
speeds (WS1, WS2), vehicle speed (VSS), coolant temperature (ECT),
intake manifold pressure (MAP), accelerator pedal position (PPS),
ignition switch position (IGN), throttle valve position (TP), air
temperature (TMP), exhaust gas oxygen (EGO) or other exhaust gas
component concentration or presence, intake air flow (MAF),
transmission gear, ratio, or mode, transmission oil temperature
(TOT), transmission turbine speed (TS), torque converter bypass
clutch 334 status (TCC), deceleration or shift mode (MDE).
Control logic or functions performed by controller 350 may be
represented by flow charts or similar diagrams in one or more
figures. These figures provide representative control strategies
and/or logic that may be implemented using one or more processing
strategies such as event-driven, interrupt-driven, multi-tasking,
multi-threading, and the like. As such, various steps or functions
illustrated may be performed in the sequence illustrated, in
parallel, or in some cases omitted. Although not always explicitly
illustrated, often one or more of the illustrated steps or
functions may be repeatedly performed depending upon the particular
processing strategy being used. Similarly, the order of processing
is not necessarily required to achieve the features and advantages
described herein, but is provided for ease of illustration and
description. The control logic may be implemented primarily in
software executed by a microprocessor-based vehicle, engine, and/or
powertrain controller, such as controller 350. Of course, the
control logic may be implemented in software, hardware, or a
combination of software and hardware in one or more controllers
depending upon the particular application. When implemented in
software, the control logic may be provided in one or more
computer-readable storage devices or media having stored data
representing code or instructions executed by a computer to control
the vehicle or its subsystems. The computer-readable storage
devices or media may include one or more of a number of known
physical devices which utilize electric, magnetic, and/or optical
storage to keep executable instructions and associated calibration
information, operating variables, and the like.
An accelerator pedal 352 is used by the driver of the vehicle to
provide a demanded torque, power, or drive command to propel the
vehicle. In general, depressing and releasing the pedal 352
generates an accelerator pedal position signal that may be
interpreted by the controller 350 as a demand for increased power
or decreased power, respectively. Based at least upon input from
the pedal, the controller 350 commands torque from the engine 314
and/or the M/G 318. The controller 350 also controls the timing of
gear shifts within the gearbox 324, as well as engagement or
disengagement of the disconnect clutch 326 and the torque converter
bypass clutch 334. Like the disconnect clutch 326, the torque
converter bypass clutch 334 can be modulated across a range between
the engaged and disengaged positions. This produces a variable slip
in the torque converter 322 in addition to the variable slip
produced by the hydrodynamic coupling between the impeller and the
turbine. Alternatively, the torque converter bypass clutch 334 may
be operated as locked or open without using a modulated operating
mode depending on the particular application.
To drive the vehicle with the engine 314, the disconnect clutch 326
is at least partially engaged to transfer at least a portion of the
engine torque through the disconnect clutch 326 to the M/G 318, and
then from the M/G 318 through the torque converter 322 and gearbox
324. When the engine 314 alone provides the torque necessary to
propel the vehicle, this operation mode may be referred to as the
"engine mode," "engine-only mode," or "mechanical mode."
The M/G 318 may assist the engine 314 by providing additional power
to turn the shaft 330. This operation mode may be referred to as a
"hybrid mode," an "engine-motor mode," or an "electric-assist
mode."
To drive the vehicle with the M/G 318 as the sole power source, the
power flow remains the same except the disconnect clutch 326
isolates the engine 314 from the remainder of the powertrain 312.
Combustion in the engine 314 may be disabled or otherwise OFF
during this time to conserve fuel. The traction battery 320
transmits stored electrical energy through wiring 354 to power
electronics 356 that may include an inverter, for example. The
power electronics 356 convert DC voltage from the battery 320 into
AC voltage to be used by the M/G 318. The controller 350 commands
the power electronics 356 to convert voltage from the battery 320
to an AC voltage provided to the M/G 318 to provide positive or
negative torque to the shaft 330. This operation mode may be
referred to as an "electric only mode," "EV (electric vehicle)
mode," or "motor mode."
In any mode of operation, the M/G 318 may act as a motor and
provide a driving force for the powertrain 312. Alternatively, the
M/G 318 may act as a generator and convert kinetic energy from the
powertrain 312 into electric energy to be stored in the battery
320. The M/G 318 may act as a generator while the engine 314 is
providing propulsion power for the vehicle 310, for example. The
M/G 318 may additionally act as a generator during times of
regenerative braking in which rotational energy from spinning
wheels 342 is transferred back through the gearbox 324 and is
converted into electrical energy for storage in the battery
320.
It should be understood that the schematic illustrated in FIG. 3 is
merely exemplary and is not intended to be limited. Other
configurations are contemplated that utilize selective engagement
of both an engine and a motor to transmit through the transmission.
For example, the M/G 318 may be offset from the crankshaft 328,
and/or the M/G 318 may be provided between the torque converter 322
and the gearbox 324. Other configurations are contemplated without
deviating from the scope of the present disclosure.
In one exemplary system when during normal operation, driver
requests are interpreted by the Vehicle System Control (VSC). These
requests include a gear selection (PRNDL) and an accelerator pedal
position (APPS) to interpret a desired wheel torque. Other driver
requests include a brake pedal position input to a brake pedal
position sensor (BPPS) that is interpreted by the Brake System
Control Module (BSCM) and a wheel torque modification request that
is sent to the VSC to adjust the final wheel torque. The
high-voltage battery electronic control module (BECM) monitors
battery characteristics including, at a battery cell level and
overall battery level, a battery temperature, terminal voltage,
current, and state of charge (SOC), and based on the battery
characteristics determines a maximum allowable discharge power
limit and a maximum allowable charge power limit. The VSC then
determines a powertrain operating point to maintain the battery
state of charge while minimizing fuel consumption and delivering
the driver requested vehicle operation. A Torque Control (TC)
controller in the VSC determines torque split such that a torque
demand is divided between engine torque and motor torque
commands.
The VSC and Motor Control Unit (MCU) communicate via a
communication bus 210 (e.g., CAN bus, Flexray bus, Ethernet bus, or
other vehicle bus) (See FIG. 2). During normal operation, the VSC
sends a motor torque commend with a desired motor torque to MCU and
MCU responds back with a driven motor torque. During a
communication fault in which the MCU losing communication with the
VSC, the VSC does not transmit the motor torque commend and does
not receive the driven torque from the MCU.
FIG. 4 is a schematic diagram of the electric power connections in
a HEV power system 400. The HEV power system includes a
motor/inverter system controller (ISC) 402 that is powered by a
traction (e.g., high-voltage) battery 404. The battery 404 may be
disconnected from the circuit via high-voltage (HV) contactors 406
and a capacitor 408 is typically coupled parallel with motor/ISC
402. Also, a Direct Current (DC) to DC converter 410 is selectively
coupled in parallel with the battery 404 to convert a high-voltage
(e.g., >100 Volts, 240V, or 300V) of the traction battery 404 to
a low-voltage (e.g., <100 Volts, 24V, or 12V) of the auxiliary
battery 412.
In an MHT configuration, the 12V system 412 is charged via the
DC/DC converter 410 and the high-voltage bus (e.g., the traction
battery 404). The high-voltage battery 404, in turn, is charged via
the high-voltage electric motor 402, or in a PHEV implementation
via a connection with a power grid (not shown).
Often systems are configured such that when communication is lost
between an MCU and VSC, the MCU will not operate the electric motor
charge the traction battery 404 that in turn would limit charging
of the auxiliary (e.g., 12V) battery 412 via the remaining energy
of the traction battery 404. As such, the traction battery 404 may
eventually become depleted due to use of high-voltage loads (e.g.,
air-conditioning load, DC/DC). Eventually, the auxiliary (e.g.,
12V) battery 412 may also become depleted resulting in a 12V bus
voltage falling below a certain threshold to keep the Engine
Control Unit (ECU) alive. This will result in a shutdown of the
vehicle (e.g., quit on road (QoR).
Here, a strategy is provided to continue to operate a vehicle
(e.g., vehicle 310 or vehicle 112) when a controller (such as an
MCU) loses communication (e.g., CAN, Ethernet, or Flexray
communication). In one illustration, an MCU loses CAN communication
with all modules including a Battery Control Module (BECM). Loss of
BECM communication is a more restrictive failure and hence, is a
superset of other possible scenarios for example, an MCU partial
CAN communication loss.
Here, the MCU operates the motor independently (i.e., without a
torque command received from a vehicle system controller (VSC)). In
a lost communication scenario, the MCU enters into an inverter
voltage maintenance mode (i.e., a desired motor torque is based on
a feedback controller to maintain an inverter voltage at a desired
set point. The VSC uses traction battery current and traction
battery voltage to estimate a motor torque in an absence of actual
feedback from MCU monitoring the motor. The VSC then corrects the
requested engine torque based on the estimated motor torque. This
ensures engine produces enough torque to meet driver demand as well
as to compensate for the electric motor load.
FIG. 5 is a flow diagram of a vehicle control system during a loss
of motor communications. In this example flow diagram, an MHT
hybrid powertrain is configured to propel the vehicle solely by
engine, and a power-split hybrid requires controlling engine speed
to a set target via generator and wheel torque is function of
engine and motor torque. Here, an FMEM strategy to operate a
vehicle in the event of MCU losing CAN communication is disclosed.
A controller branches on detection of a communication failure in
block 502. If the no communication failure is detected, the
controller exits. In the event of MCU communication failure (e.g.,
CAN communication failure that may result in a flag being set in
all associated modules), in block 504 the controller in the VSC
pulls-up (e.g., starts) the engine (if the engine was not
operating) and inhibits engine stop-start during operation and
proceeds to block 506. Stop-start operation allows a controller to
shut off the internal combustion engine (ICE) when a demand drops
below a threshold (e.g., when the vehicle is at stop light, stopped
in traffic, or even coasting down an incline) and automatically
starts the ICE when a demand exceeds the threshold (e.g., when the
gas pedal is depressed to accelerate the vehicle). By stopping the
ICE when the demand is below the threshold, fuel efficiency is
increased. The communication failure may be detected via multiple
ways, for example, some communication strategies an acknowledgement
is automatically sent from the receiving module upon reception of a
packet of data. Also, some of the modules communicate with other
modules on a regular or semi-regular basis as such a up/down timer
may be configured generate an interrupt upon an overflow/underflow
and to reset upon reception of an acknowledgement or other
communication message. The reset of the up/down counter may be
include loading a predetermined value and counting down or up until
an underflow/overflow occurs, or alternatively the counter may load
zeroes or 1 s (e.g., 0.times.FFFF) upon reset, and count up/down
until the timer matches the predetermined value loaded into a match
register.
Once the communication failure is detected, the MCU controller in
block 506 enters into an inverter voltage maintenance mode in which
the inverter output voltage is maintained at a current voltage
level. In block 508 the VSC controller estimates a desired motor
torque based on a feedback controller in which the inverter voltage
is maintained at a desired set point. Here, the set point is stored
inside MCU and doesn't need any communication from VSC.
e=V.sub.set-V.sub.inv (1) .tau..sub.mtr.sup.des=f(e) (2) In which
V.sub.set is the desired inverter voltage set point, V.sub.inv is
the inverter voltage and .tau..sub.mtr.sup.des is the desired motor
torque. The function f is a feedback controller to calculate
desired motor torque as function of voltage error. One of the
implementation of this feedback controller is a PID controller that
may be represented by equation 3 below.
f=K.sub.Pe+K.sub.I.intg.edt+K.sub.D (3) In which K.sub.P, K.sub.I
and K.sub.D are the PID gains for the feedback controller.
Generally, a loss in communication with the BECM results in a loss
of traction battery State of Charge (SOC) information being
provided to the MCU. As the traction battery SOC is highly
correlated with a voltage of the traction battery when the battery
chemistry is Li-Ion, maintaining a set voltage is very similar to
maintaining a desired SOC in the traction battery. The closed loop
control is performed on the inverter voltage (i.e. terminal voltage
at the motor) which is available to the MCU based on a voltage
sensor without battery voltage over the communication link from the
BECM.
Also, the desired motor torque may be clipped on the positive side
to a calibratable based on nominal engine friction torque. Without
this clip, it is possible to create an unintended acceleration for
extremely low driver demands as engine will not be able to reduce
torque below its friction torque. The VSC estimates the motor
torque .tau..sub.mtr.sup.est based on battery current and voltage
as shown in the equation below P.sub.Bat=V.sub.Bat*I.sub.BAT
(4)
.tau..omega. ##EQU00001## In which, V.sub.Bat is the HV battery
voltage, I.sub.Bat is the HV battery current and (.omega..sub.eng
is the engine speed. The engine speed may be used as a substitute
for motor speed in equation 5 as motor speed is not available due
to communication failure with MCU. After the controller proceeds to
block 510 in which the requested engine torque
.tau..sub.eng.sup.req may be then corrected for the estimated motor
torque as shown in equation 6.
.tau..sub.eng.sup.req=.tau..sub.DD+.tau..sub.mtr.sup.est (6) In
which, .tau..sub.DD is the driver demand.
Control logic or functions performed by controller may be
represented by flow charts or similar diagrams in one or more
figures. These figures provide representative control strategies
and/or logic that may be implemented using one or more processing
strategies such as event-driven, interrupt-driven, multi-tasking,
multi-threading, and the like. As such, various steps or functions
illustrated may be performed in the sequence illustrated, in
parallel, or in some cases omitted. Although not always explicitly
illustrated, one of ordinary skill in the art will recognize that
one or more of the illustrated steps or functions may be repeatedly
performed depending upon the particular processing strategy being
used. Similarly, the order of processing is not necessarily
required to achieve the features and advantages described herein,
but are provided for ease of illustration and description. The
control logic may be implemented primarily in software executed by
a microprocessor-based vehicle, engine, and/or powertrain
controller, such as controller. Of course, the control logic may be
implemented in software, hardware, or a combination of software and
hardware in one or more controllers depending upon the particular
application. When implemented in software, the control logic may be
provided in one or more computer-readable storage devices or media
having stored data representing code or instructions executed by a
computer to control the vehicle or its subsystems. The
computer-readable storage devices or media may include one or more
of a number of known physical devices which utilize electric,
magnetic, and/or optical storage to keep executable instructions
and associated calibration information, operating variables, and
the like.
The processes, methods, or algorithms disclosed herein can be
deliverable to/implemented by a processing device, controller, or
computer, which can include any existing programmable electronic
control unit or dedicated electronic control unit. Similarly, the
processes, methods, or algorithms can be stored as data and
instructions executable by a controller or computer in many forms
including, but not limited to, information permanently stored on
non-writable storage media such as Read Only Memory (ROM) devices
and information alterably stored on writeable storage media such as
floppy disks, magnetic tapes, Compact Discs (CDs), Random Access
Memory (RAM) devices, and other magnetic and optical media. The
processes, methods, or algorithms can also be implemented in a
software executable object. Alternatively, the processes, methods,
or algorithms can be embodied in whole or in part using suitable
hardware components, such as Application Specific Integrated
Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state
machines, controllers or other hardware components or devices, or a
combination of hardware, software and firmware components.
While exemplary embodiments are described above, it is not intended
that these embodiments describe all possible forms encompassed by
the claims. The words used in the specification are words of
description rather than limitation, and it is understood that
various changes can be made without departing from the spirit and
scope of the disclosure. As previously described, the features of
various embodiments can be combined to form further embodiments of
the invention that may not be explicitly described or illustrated.
While various embodiments could have been described as providing
advantages or being preferred over other embodiments or prior art
implementations with respect to one or more desired
characteristics, those of ordinary skill in the art recognize that
one or more features or characteristics can be compromised to
achieve desired overall system attributes, which depend on the
specific application and implementation. These attributes may
include, but are not limited to cost, strength, durability, life
cycle cost, marketability, appearance, packaging, size,
serviceability, weight, manufacturability, ease of assembly, etc.
As such, embodiments described as less desirable than other
embodiments or prior art implementations with respect to one or
more characteristics are not outside the scope of the disclosure
and can be desirable for particular applications.
* * * * *